Protective pallet assembly

ABSTRACT

A timepiece escapement pallet lever carrying pallet pins and journaled proximate a frame support post for pivotal oscillation within a predetermined angle to time a driven escape wheel by intermittent engagement of escape wheel teeth with the pallet pins. Bumpers extend from one side of the pallet lever to bear against the support post upon pivoting of the pallet lever beyond extremes of the oscillation angle to prevent damage to the pallet pins.

United States Patent [72] Inventor Robert R. Lawson 1,535,286 4/1925Bates.. 58/116 Somerset, Wis. 3,137,122 6/1964 Dinerstein et al 58/116 11 pp 15,759 FOREIGN PATENTS g 'ff 3 1,316,624 12/1962 France 58/116 [73]Assignee The Bunker-Ramo Corpor ti 373,703 8/1963 Switzerland 58/1 16 Ok B k, Ill, Primary Examiner- Richard B. Wilkinson AssistantExaminer-Stanley A. Wal Attorney-Frederick M. Arbuckle [54] PROTECTIVEPALLET ASSEMBLY 10 Claims, 4 Drawing Figs. [52] U.S.Cl 58/116 ABSTRACT:A timepiece escapernent pallet lever carrying 1 Cl 15/00 pallet pins andjournaled proximate a frame support post for [50] FiQld O'Sfill'lfh58/116; pivotal oscillation within a predetermined an le to time adriven escape wheel by intermittent engagement of escape wheel teethwith the allet ins. Bum ers extend from one [56] 'f c'ted side of thepallet lever to be r against the support post upon UNITED STATES PATENTSpivoting of the pallet lever beyond extremes of the oscillation1,343,798 58/116 angle to prevent damage to the pallet pins.

6/1920 Toda PATENIED JUN 8 l9?! FIG. I "PRIOR ART" INVENTOR Robert R.Lawson .FIG. 2

PROTECTIVE PALLET ASSEMBLY SUMMARY OF THE INVENTION This inventionrelates generally to timepiece escapements, and more particularly, to aprotective pallet assembly therein.

Timepiece configuration and gear train geometry usually require that theescapement mechanism be located at or near the periphery of thetimepiece support framework. A framework support post is often locatedproximate to the escapement mechanism to afford some protection thereof.Nevertheless, portions of the escapement mechanism remain unprotected;for example, the pallet escape lever generally has an outermostperiphery which extends beyond or to the outer edges of the framework atan extreme of its pivotal oscillation. The pallet escape lever carries apair of delicate pallet pins which engage the teeth of a driven escapewheel for timing thereof. A problem exists in that prior to assembly ofthe timepieces into their protective casings, the pallet pins are easilybent out of proper engagement disposition. This to be caused byinadvertent placement down of the timepiece upon the exposed peripheryof the pallet lever or by accidental touching thereof by the fingers ofthe assemblers. This caused the pallet lever to pivot beyond itsoscillation limits to bend the pallet pins. A high rate of rejectsresulted.

Therefore, to overcome the foregoing and other difficulties of the priorart, new and improved means of protecting the pallet escape lever arerequired. Preferably, such protective means are afforded withoutaddition to the support framework or redesign of the timepiece geometry.To this end, the present invention envisions modification of existingpallet escape levers to provide a novel protection means. In accordancewith the present invention, the pallet escape lever is modified toprovide a pair of spaced bumpers defining therebetween an open portionof the lever which receives the framework support post therein. Thebumpers have a clearance with respect to the support post, at theoscillation extremes, which is within the deformation limits of thepallet pins. Upon pivoting of the pallet escape lever beyond normaloscillation limits a distance sufficient to deflect a pin one diameter,the bumpers will bear against the post to prevent damage to the pins.The configuration of the pallet escape lever, according to the presentinvention, is asymmetric with respect to a central axis to provideportions balancing the bumpers. Also, the outermost periphery of theinvented pallet lever configuration is within a radius concentric withthe movement center to eliminate any outstanding projection atoscillation extremes.

Thus, one of the objects of this invention is to provide improvedprotection for a timepiece escapement mechanism.

It is an object of this invention to utilize the existing supportframework together with a modification of an existing pallet leverconfiguration to provide protection therefore.

Another object is to provide pallet escape lever protection withoutaddition to the timepiece support framework or modification of thetimepiece geometry.

Still another object is to provide a modification to a pallet escapelever which protects against movement beyond oscillation extremes byengagement against the timepiece support framework.

Yet another object is the provision of a protective pallet levermodification which is easily achieved and susceptible to economical massproduction manufacturing techniques.

An object of this invention is the provision of a pallet escape levermodified for protection and balance thereof.

Further and other objects, and a more complete understanding of theinvention may be had by referring to the following description andclaims, taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS For the purpose of illustrating theinvention, there is shown in the drawings a form which is presentlypreferred, it being understood, however, that this invention is notnecessarily limited to the precise arrangement and instrumentality thereshown.

FIG. I is a partial plan view showing a portion ofa prior-art timepieceescapement mechanism.

FIG. 2 is a partial side elevational view of a timepiece escapementmechanism having a protective pallet assembly therefore according to thepresent invention.

FIG. 3 is a cross-sectional view of the escapement mechanism andprotective pallet assembly of FIG. 2 taken along line 3-3 thereof.

FIG. 4 is a plan view of a form of pallet lever according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The best mode presentlycontemplated of carrying out this invention, which is an improvement inprior-art timepiece escape mechanisms, is set forth in the writtendescription and drawings wherein parts relating to the improvement areparticularly pointed out together with those prior-art parts asnecessarily cooperate with the improvement and as are necessary to acomplete understanding and description of the present invention.Referring to the drawings in detail, wherein like numerals indicate likeelements, there is shown in FIG. 1 an illustration of a prior-arttimepiece escapement mechanism indicated generally by the numeral 10.Generally, as illustrated, the timepiece support frames include two ormore frame plates, such as the one shown at 12, which are spaced apartby support posts such as the one indicated at 14. The escapementmechanism shown is typical and includes escape wheel 20, balance wheel30 and pallet lever 40, all journaled on shafts 25,35 and 45,respectively, between frame plates 12 in the manner illustrated at FIG.2. As is well known in the art, the escapement wheel 20 is driven by atimepiece gear train (such as that partially visible at 22 in FIG. 2)and timed by intermittent engagement of the teeth 26 with the palletpins 46, which are carried on pallet lever 40. It is understood thatbalance wheel 30 is driven, with rotary oscillations, by the palletlever 40 through interaction between fork slot configuration 48 andimpulse pin 38. Oscillations of balance wheel 30 are timed by ahairspring such as shown at 32 in FIG. 2. Interaction of guard pin 47and roller crescent 37 prevent an out of phase condition between forkslot 48 and impulse pin 38. The pallet lever 40 will oscillate back andforth, as indicated by the double-headed arrow of FIG. 1, in a customarymanner to time the escape wheel 20. The usual regulator fan and rateadjusting means 33 shown in FIG. 2 may be utilized to change theoscillation period if necessary to correct the timing. The phantomrepresentation in FIG. I of pallet lever 40 indicates its position atone extreme of the oscillation angle 6. It is readily apparent from FIG.I that an outer peripheral corner of the pallet lever 40 is exposed andthat the pallet lever 40 can pivot beyond the extremes of theoscillation angle 0. The pallet pins 46 are delicate and have a specificspacing for the proper timing of escape wheel 20. It is readilyunderstood that the pins 46 are highly susceptible to damage in theexposed and unprotected assembly of FIG. 1.

A protective pallet assembly, according to the present invention, is setforth herein with references to FIGS. 2 through 4. Parts of theescapement mechanism shown in FIGS. 2 and 3 which are identical to thoseshown in FIG. I are indicated by identical numerals, and no furtherdescription of those parts is believed necessary. However, the palletlever 40', to which the improvement relates, according to the presentinvention, is particularly pointed out by the following detaileddescription of pallet lever 40' parts.

The pallet lever 40', in accordance with the present invention, has amarkedly different configuration from that of the prior-art pallet lever40; however, both may be metal punchings which are force fitted, each onan individual shaft 45 which extends perpendicularly therethrough forpivoting about an axis indicated at (X) in FIG. 4. Note with referenceto FIG. 3 that the shaft 45 and its pivot axis are parallel andrelatively proximate to the support post 14. The pallet pins 46 arespaced apart in the projections 50, SI at one side of the central axis(Z-Z) through the pallet lever 40 as shown in the detail of FIG. 4. Thepallet lever 40' also includes at one end a guard pin 47 and a fork slotconfiguration 48 for interaction with the roller crescent 37 and impulsepin 38 of the balance wheel 30, in the conventional manner.

Bumper means for bearing against the post 14 upon pivoting beyondextremes of the oscillation angle are provided by the spaced bumper armmembers 60, 61 which extend outwardly at the side of the central axis(Z-Z) opposite that of the projections 50, 51. The bumper arm members60, 6I define therebetween an open portion 63 of the lever, within whichthe post I4 is partially received as shown. The open portion 63 extendsover an arc concentric with axis (X), between the bumper points 65, 66at the ends of the arm members 60, 61 respectively. The opening 63naturally must be sufficient in extent to permit unimpaired oscillationbetween the extremes of oscillation angle 0. The pallet pins 46 are of aresilient material which springs back without damage when displaced onepin diameter or less at the escape wheel 30. To insure unimpairedoscillation, the resiliency of pins 46 is taken ad vantage of and aclearance is provided between the arm members 60, 61 and post 14 at thecorresponding extremes of the oscillation angle 9. With reference toFIG. 3, notice the clearance (C) between the phantom edge of arm member60 and the post 14. Clearance (C) may be chosen by an ap propriateextent of the arc of open portion 63 to allow a displacement of pins 46at the escape wheel of one diameter of the pins, or less if desired.

The extent of the are between bumper points 65, 66 may be determined byreference to FIG. 4. Tangents 70, 71 between the axis (X) and post 14subtend an arc length 72 between the tangential points 73, 74 on post14. Projections 75, 76 of tangents between axis (X) and diametricallyopposed points on the pins 46 may be transposed as indicated in FIG. 4to subtend two are lengths 78. The total of arc lengths 80 are subtendedby the oscillation angle, that is, each separate arc length 80 beingequal to one-half 6. Thus, the extent of the arc of open portion 63 isreadily understood to be a summation of arc lengths 72, 78 and 80, asshown in FIG. 4. Therefore, the lever 40' may oscillate between theextremes of oscillation angle 0 with a clearance (C) at each extremesufficient to allow displacement of the pallet pins 46 one pin diameterat the escape wheel 20.

Note, with reference to FIG. 4, that the pallet lever 40 is asymmetricwith respect to the central axis (2-2). The asymmetry is to providebalanced areas on each side of the axis (2-2). The periphery 90 at theoutermost and of lever 40, has a configuration within a radius (R) whichis concentric with the axis (X). With reference to FIG. 3 it may be seenthat the periphery 90 is well within the confines of the frame plates 12at any extreme of the oscillation angle.

Timing operation of the timepiece escapement shown in FIGS. 2 and 3 isconventional, as described beforehand. How-- ever, the protective palletassembly thereof, in accordance with the present invention, preventsdamage to the delicate pallet pins 46. In the first instance there is noprotrusion or exposure of the outermost periphery 90 of the lever 40 ateither extreme of angle 0. The clearance (C) between each bumper armmember 60, 61 and post 14, at each extreme of angle 0, allows unimpairedtiming oscillation. In the event that lever 40' is forced beyond eitherextreme of angle 0, one of the pins 46 which is engaged at teeth 26 ofescape wheel 20 will be displaced up to the limit of one diameter of thepin. Further displacement is prevented by the contact of one of thebumper points 65, 66, of arm members 60, 61 against a respectivetangential point 73, 74 at post 14. The post 14, being one of thesubstantial and principle structural members of the timepiece supportframe, bears against a respective one of the arm members 60, 61, andprevents damage to either of the pins 46. Resiliency of the pins 46 willreturn the pins to their correct timing positions, once the force thatcauses the pivoting beyond the extremes of angle 0 is released. In thismanner, a protective pallet assembly, dependent upon existing majorstructural support frame members, is provided in accordance with thepresent invention.

While a particular embodiment of the invention has been illustrated anddescribed, it will be obvious to those skilled in the timepiece art thatchanges and modifications may be made without departing from theinvention in its broader aspects and, therefore, the aim in the appendedclaims is to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

I claim:

1. In a timepiece escapement within a frame having a support post, aprotective pallet, comprising:

an escape lever carrying a pair of pallet pins and journaled on a shaftin said frame to pivot about an axis proximate said post for pivotaloscillation within a predetermined angle, and:

bumper means on said lever cooperating with said support post forlimiting the pivoting of said lever beyond extremes of said angle toprotect said pins.

2. A pallet according to claim 1 wherein said bumper means are providedby a pair of spaced bumper arm members of said lever definingtherebetween an open portion of said lever for reception of said posttherein, said open portion extending over an arc concentric with saidaxis, said are being of an extent sufficient to include an arc lengthsubtended by said angle and an arc length subtended between tangentsfrom said axis to said post, each of said arm members extending outwardfrom said axis a radial distance sufficient to meet the tangentialpoints of said tangents to bear against said post thereat upon pivotingof said lever beyond a corresponding extreme of said angle,respectively.

3. A pallet according to claim 2 wherein each of said arm members has aclearance with respect to said post at said corresponding extreme ofsaid angle, said clearance being sufficient to allow deflection of saidpins within their elastic limit, and said clearance being provided bysaid are extent also including arc lengths equivalent to those subtendedby projections of tangents from said axis to diametrically opposedselected points on said pins.

4. A pallet according to claim 3 wherein said lever is asymmetric withrespect to a central axis to provide balance therefore.

5. A pallet according to claim 4 wherein said lever includes anoutermost periphery with respect to said frame, said periphery having aconfiguration within and conformity to a radius concentric with saidaxis and within said frame to eliminate exposure therebeyond of saidperiphery at any extreme of said angle during said oscillation forprotection thereof within said frame.

6. A pallet according to claim 4 wherein said pins and arm members areon opposite sides of said axis.

7. In a timepiece escapement having a driven escape wheel timed by apair of pallet pins oscillating in and out of engagement therewith, aprotective assembly therefore, comprising in combination:

a pair of frame plates;

a support post spacing said plates apart;

a pallet escape lever journaled on a shaft between said plates on anaxis proximate said post, said lever carrying said pallet pins forpivotal oscillation about said axis within a predetermined angle, and;

bumper means extending from said lever for bearing against said postupon pivoting of said lever substantially beyond extremes of said angleto prevent damage to said pins.

8. A pallet according to claim 7 wherein said bumper means are providedby bumper arm members of said lever, each of said arm members having aclearance with respect to said post at a corresponding extreme of saidangle sufficient to allow deflection of said pins not more than theirelastic limit at said escape wheel,

9. A pallet according to claim 7 wherein said lever is asymmetric withrespect to a central axis to provide portions balancing said bumpermeans, and wherein said pins and bumper means are on opposite sides ofsaid axis.

10. A pallet according to claim 7 wherein said lever has an 5 forprotecnon thereof outermost periphery with respect to said plates, saidperiphery having a configuration within and conforming to a radiusconcentric with said shaft and within said plates to prevent exposuretherebeyond of said periphery at extremes of said angle hin said plates.

1. In a timepiece escapement within a frame having a support post, aprotective pallet, comprising: an escape lever carrying a pair of palletpins and journaled on a shaft in said frame to pivot about an axisproximate said post for pivotal oscillation within a predeterminedangle, and: bumper means on said lever cooperating with said supportpost for limiting the pivoting of said lever beyond extremes of saidangle to protect said pins.
 2. A pallet according to claim 1 whereinsaid bumper means are provided by a pair of spaced bumper arm members ofsaid lever defining therebetween an open portion of said lever forreception of said post therein, said open portion extending over an arcconcentric with said axis, said arc being of an extent sufficient toinclude an arc length subtended by said angle and an arc lengthsubtended between tangents from said axis to said post, each of said armmembers extending outward from said axis a radial distance sufficient tomeet the tangential points of said tangents to bear against said postthereat upon pivoting of said lever beyond a corresponding extreme ofsaid angle, respectively.
 3. A pallet according to claim 2 wherein eachof said arm members has a clearance with respect to said post at saidcorresponding extreme of said angle, said clearance being sufficient toallow deflection of said pins within their elastic limit, and saidclearance being provided by said arc extent also including arc lengthsequivalent to those subtended by projections of tangents from said axisto diametrically opposed selected points on said pins.
 4. A palletaccording to claim 3 wherein said lever is asymmetric with respect to acentral axis to provide balance therefore.
 5. A pallet according toclaim 4 wherein said lever incluDes an outermost periphery with respectto said frame, said periphery having a configuration within andconformity to a radius concentric with said axis and within said frameto eliminate exposure therebeyond of said periphery at any extreme ofsaid angle during said oscillation for protection thereof within saidframe.
 6. A pallet according to claim 4 wherein said pins and armmembers are on opposite sides of said axis.
 7. In a timepiece escapementhaving a driven escape wheel timed by a pair of pallet pins oscillatingin and out of engagement therewith, a protective assembly therefore,comprising in combination: a pair of frame plates; a support postspacing said plates apart; a pallet escape lever journaled on a shaftbetween said plates on an axis proximate said post, said lever carryingsaid pallet pins for pivotal oscillation about said axis within apredetermined angle, and; bumper means extending from said lever forbearing against said post upon pivoting of said lever substantiallybeyond extremes of said angle to prevent damage to said pins.
 8. Apallet according to claim 7 wherein said bumper means are provided bybumper arm members of said lever, each of said arm members having aclearance with respect to said post at a corresponding extreme of saidangle sufficient to allow deflection of said pins not more than theirelastic limit at said escape wheel.
 9. A pallet according to claim 7wherein said lever is asymmetric with respect to a central axis toprovide portions balancing said bumper means, and wherein said pins andbumper means are on opposite sides of said axis.
 10. A pallet accordingto claim 7 wherein said lever has an outermost periphery with respect tosaid plates, said periphery having a configuration within and conformingto a radius concentric with said shaft and within said plates to preventexposure therebeyond of said periphery at extremes of said angle forprotection thereof within said plates.